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Anthony Bloch

Anthony Bloch
Department of Mathematics, The University of Michigan, Ann Arbor, MI 48109
University of Michigan, USA
Alexander Ziwet Collegiate Professor of Mathematics, The University of Michigan


Fernandez O. E., Mestdag T., Bloch A. M.
A generalization of Chaplygin’s Reducibility Theorem
2009, vol. 14, no. 6, pp.  635-655
In this paper we study Chaplygin’s Reducibility Theorem and extend its applicability to nonholonomic systems with symmetry described by the Hamilton–Poincare–d’Alembert equations in arbitrary degrees of freedom. As special cases we extract the extension of the Theorem to nonholonomic Chaplygin systems with nonabelian symmetry groups as well as Euler–Poincaré–Suslov systems in arbitrary degrees of freedom. In the latter case, we also extend the Hamiltonization Theorem to nonholonomic systems which do not possess an invariant measure. Lastly, we extend previous work on conditionally variational systems using the results above. We illustrate the results through various examples of well-known nonholonomic systems.
Keywords: Hamiltonization, nonholonomic systems, reducing multiplier
Citation: Fernandez O. E., Mestdag T., Bloch A. M.,  A generalization of Chaplygin’s Reducibility Theorem, Regular and Chaotic Dynamics, 2009, vol. 14, no. 6, pp. 635-655
Bloch A. M., Gurfil P., Lum K. Y.
The Serret–Andoyer Formalism in Rigid-Body Dynamics: II. Geometry, Stabilization, and Control
2007, vol. 12, no. 4, pp.  426-447
This paper continues the review of the Serret–Andoyer (SA) canonical formalism in rigid-body dynamics, commenced by [1], and presents some new results. We discuss the applications of the SA formalism to control theory. Considerable attention is devoted to the geometry of the Andoyer variables and to the modeling of control torques. We develop a new approach to Stabilization of rigid-body dynamics, an approach wherein the state-space model is formulated through sets of canonical elements that partially or completely reduce the unperturbed Euler–Poinsot problem. The controllability of the system model is examined using the notion of accessibility, and is shown to be accessible. Based on the accessibility proof, a Hamiltonian controller is derived by using the Hamiltonian as a natural Lyapunov function for the closed-loop dynamics. It is shown that the Hamiltonian controller is both passive and inverse optimal with respect to a meaningful performance-index. Finally, we point out the possibility to apply methods of structure-preserving control using the canonical Andoyer variables, and we illustrate this approach on rigid bodies containing internal rotors.
Keywords: nonlinear stabilization, Hamiltonian control systems, Lyapunov control
Citation: Bloch A. M., Gurfil P., Lum K. Y.,  The Serret–Andoyer Formalism in Rigid-Body Dynamics: II. Geometry, Stabilization, and Control, Regular and Chaotic Dynamics, 2007, vol. 12, no. 4, pp. 426-447

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